Problems that only humans will ever be able to solve
Informally, AI-complete problems are the most difficult problems for an AI. The concept is not mathematically defined yet, as e.g. NP-complete problems. However, intuitively, these are the problems that require a human-level or general intelligence to be solved.

Real natural language understanding is believed to be an AI-complete problem (this is also discussed in the paper Making AI Meaningful Again by Jobst Landgrebe and Barry Smith, 2019). There are a lot more AI-complete problems. For example, problems that involve emotions.